Field of the Invention
The invention relates to a polycaprolactone composition which has been blended with another resin, that is, (B-1) a thermoplastic resin and a tackifier or (B-2) a chlorinated polyolefin.
Having a melting point as low as 60.degree. C. and being easy in processing, polycaprolactone is widely used. However, due to lack of sufficient flexural resistance and tackiness, it is not applied to moldings such as a core material for shoes.
It is an object of this invention to provide a polycaprolactone resin composition which is free of the above-mentioned drawbacks and is superior in flexural resistance and tackiness.
The invention relates to a synthetic resin composition which comprises (A) 100 parts by weight of polycaprolactone and (B-1) 10 to 70 parts by weight of a thermoplastic resin and 1 to 30 parts by weight of a tackifier, or (B-2) 10 to 70 parts by weight of a chlorinated polyolefin.
The polycaprolactone used in this invention may be produced according to the process as disclosed in Japanese Patent Application No. 126221/1979.
The polymer used in this invention preferably has a number-average molecular weight from 5,000 to 200,000 especially from 10,000 to 200,000.
The thermoplastic resin other than polycaprolactone is used in this invention in an amount from 10 to 70 parts by weight for 100 parts by weight of polycaprolactone. The thermoplastic resin includes polyolefins such as polyethylene, polypropylene, vinyl chloride resin, and ethylene-vinyl acetate copolymer; and styrene resins such as polystyrene. Preferable among them are chlorinated polyolefins such as chlorinated polyethylene. Examples of chlorinated polyolefins include chlorinated polyethylene, chlorinated polypropylene, and chlorinated polybutene. The chlorinated polyethylene is obtained by chlorinating polyethylene, ethylene-propylene copolymer or ethylene-butene copolymer and contains 25 to 45 wt% of chlorine. The chlorinated polypropylene is obtained by chlorinating isotactic polypropylene or atactic polypropylene and contains 15 to 35 wt% of chlorine.
The resin composition of this invention is a polycaprolactone resin composition which has the low-temperature processability of polycaprolactone and has superior flexural resistance and tackiness.
According to this invention, the use of a tackifier is indispensable. Examples of such tackifier include rosin, maleic rosin, ester gum, ester gum H, polyterpene resin, C.sub.5 petroleum resin, C.sub.9 petroleum resin, dicyclopentadiene petroleum resin, styrene resin, alkylphenolic resin, and terpene phenolic resin. This tackifier resin is used in an amount from 1 to 30 parts by weight based on 100 parts by weight of polycaprolactone.
The composition of this invention may be incorporated as required with slip agent, stabilizer, pigment, etc. which are commonly added to thermoplastic resin compositions. It is preferable to add an epoxy stabilizer or lead stabilizer which is commonly used for chlorinated polyolefins.
The resin composition of this invention is useful as a molding material. It may be used, for example, as a shoe core material in the form of a sheet and as a hot melt adhesive.
The foregoing concerns the composition where components (A) and (B-1) have been blended. When a chlorinated polyolefin (B-2) is used as the thermoplastic resin, the tackifier may not be contained in the composition according to the invention. As the chlorinated polyolefin, there are preferably used the above mentioned embodiments. The combination between (A) and (B-2) is improved in point of flexural resistance and further possesses processability of polycaprolactone per se which can be attained even at a low temperature. The amount of the component (B-2) is 10 to 70 parts by weight, based on 100 parts by weight of (A).